Spinal stenosis, as well as spondylosis, spondylolisthesis, osteoarthritis, scoliosis and other degenerative phenomena may be the cause of back pain, and may be caused by a narrowing of the spinal canal or foramina that result in stress acting on the spinal cord and/or nerve roots.
One of the methods for resolving back pain involves decompression, the removal of bony elements causing the pain, and fusion of two or more adjacent vertebrae. Unfortunately, fusion tends to have significant shortcoming and may cause the problem to migrate to adjacent vertebral components. Among the non-fusion solutions are disc replacement, dynamic stabilization systems and inter-spinous process implants.
Spinal implants with the capability of height adjustment are known. For example, U.S. Pat. Nos. 6,045,579, 6,080,193 and 6,576,016 to Hochshuler et al (issued Apr. 4, 200, Jun. 27, 2000 and Jun. 10, 2003, respectively) describe an adjustable height fusion device for promoting a spinal fusion between neighboring vertebrae. The device is located within the intervertebral disc space and includes a pair of engaging plates for contacting the vertebrae. An alignment device is used to alter the vertical distance between the engaging plates to customize the apparatus to fit a given patient. In one embodiment, the alignment device includes a pair of struts having a predetermined height and extending between the engaging plates from an anterior end to a posterior end of the apparatus. In another embodiment, the alignment device includes a rotatable connector and cam pins for adjusting the distance between the engaging plates. The alignment device is preferably adapted to vary the distance between the engaging plates such that the height of the apparatus proximate the anterior end is greater than that proximate the posterior end whereby the natural lordosis of the spine is maintained after the apparatus is installed.
However, these prior art devices must be adjusted prior to or during the installation and are not capable of post-operative adjustment.